The bonding performance of basalt fiber-reinforced polymer and concrete substrate has a significant effect on the reliability of externally strengthened existing concrete structure, due to being the most vulnerable element to failure in this fiber-reinforced polymer–concrete strengthening system. Its failure can result in the failure of the whole structure. Although many previous researchers have been interested in the tensile bonding strength of carbon fiber-reinforced polymer and glass fiber-reinforced polymer–concrete interface, that of basalt fiber-reinforced polymer–concrete interface has been very limited. Thus, the objective of this study is to experimentally assess the tensile bonding strength of the basalt fiber-reinforced polymer–concrete interface. The effects of high temperature, freezing–thawing cycles, type of resin, and concrete crack widths on the tensile bonding strength are also investigated. The pull-off experiment is conducted according to ASTM D7522/D7522M-15. A total of 205 core specimens of 50 mm diameter and 10 mm depth were taken from 41 concrete beams. The experimental results illustrate that both freezing–thawing and high-temperature condition have a substantial effect on the bonding strength of the basalt fiber-reinforced polymer–concrete interface. Bonding strength was decreased within the range of about 9%–30% when the number of freezing–thawing cycles increases from 100 to 300; likewise, it was decreased up to 30% when the exposure temperature rises to 200°C. Also, the specimens which were repaired to close their cracks by epoxy resin had no significant effect on the bonding strength of basalt fiber-reinforced polymer–concrete interface, when the specimens had crack width of less than 1.5 mm.
A review on the tensile properties of natural fiber reinforced polymer composites